Page 50 - Start Up Mathematics_6

(d) Since, 108 = 108 × 1 108 = 54 × 2 108 = 36 × 3

108 = 27 × 4 108 = 18 × 6 108 = 12 × 9
Therefore, factors of 108 are 1, 2, 3, 4, 6, 9, 12, 18, 27, 36, 54 and 108.
Example 2: Match the items in column I with the items in column II.
Column I Column II

(a) 42 (i) Multiple of 8
(b) 15 (ii) Multiple of 7
(c) 16 (iii) Multiple of 9

(d) 20 (iv) Factor of 30
(e) 25 (v) Factor of 50
(f) 18 (vi) Factor of 20
Solution: (a) (ii), (b) (iv), (c) (i), (d) (vi), (e) (v), (f) (iii)

Example 3: Find all the multiples of 13 up to 100.
Solution: Multiples of 13 up to 100 are:
13 × 1 = 13 13 × 2 = 26 13 × 3 = 39 13 × 4 = 52

13 × 5 = 65 13 × 6 = 78 13 × 7 = 91

EXERCISE 3.1

1. Write all the factors of the following numbers:
(a) 20 (b) 36 (c) 51 (d) 64 (e) 144 (f) 729
2. Write the first five multiples of following numbers:
(a) 7 (b) 13 (c) 17 (d) 15
3. Write all the multiples of 11 up to 100.
4. Find the factors of 20 using the activity method.

Types of Numbers

Even numbers

Any number which is divisible by 2 is called an even number. Examples of even numbers are
0, 2, 4, 6, 8, ..., etc.

Odd numbers
Numbers which are not divisible by 2 are called odd numbers. Examples of odd numbers are
1, 3, 5, 7, 9, ..., etc.

Prime numbers
The numbers other than 1 whose only factors are 1 and the number itself are called prime numbers.

Examples of prime numbers are 2, 3, 5, 7, 11, 13, ... as these do not have factors other than
1 and the number itself.

• The smallest prime number is 2.
• 2 is the only even number which is prime.

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